Question

When I want to loop through an array and add a string behind every element,

I can either

for(var x in array){
 array[x] += "string";  
}

or

for(var x, y = array.length; x<y; x++){
 array[x] += "string";  
}

But is there any difference in terms of performance between these 2 for loops?

Answer 1

It is recommended that you don’t use for ... in to iterate over arrays.

i.e. Why is using "for…in" with array iteration a bad idea?

You should use for ... in to iterate over object properties only.